A portable information terminal is not capable of providing various functions such as those furnished by a general computer since it must be as small as possible. Also, since current consumption and the weight of the portable information terminal must be reduced, it is difficult to install an auxiliary storage device such as a hard disk drive on the portable information terminal. Accordingly, portable information terminals typically use a small capacity ROM and RAM or a memory having similar characteristics. The ROM is low-priced, but the programs recorded thereon cannot be changed. In addition, although a RAM can easily change the programs recorded thereon, it is expensive and can be easily damaged by power failure.
Most portable information terminals can provide only a small number of programs and it is costly to add a new program or change the program that is already provided. There are also portable information terminals on which programs cannot be added or changed and portable information terminals on which only some programs can be added or changed. The portable information terminal is not only used as a simple electronic pocketbook but can also be used to conduct business outside the office. Accordingly, in order for the portable information terminal to be employed for business, it should be possible to install powerful programs necessary for business and also to change or add programs to suit the user's business needs.
FIG. 1 is a block diagram of the configuration of a conventional portable information terminal. Referring to FIG. 1, the conventional information terminal is comprised of a ROM 100, a RAM 102, a PCMCIA card 104, a power supply 106, a decoder 108, an optional connector 110, a connector receptacle 112, a PCMCIA card receptacle 114 and a controller 116. The ROM 100 stores predetermined program data and the RAM 102 stores a utility program that is operated to enable replacement of the program recorded in the ROM 100 with a new program. The PCMCIA card 104 stores the new programs which replace programs recorded in the ROM 100 and the utility program for updating the new program. In addition, the decoder 108 is connected to the power supply 106 and to the ROM 100 for determining the available power and selectively applying power to the ROM 100 based upon the power determination. The optional connector 110 is used to inform the terminal that the PCMCIA card 104 is inserted using a combination of specific bits. Connector receptacle 112 connected to the decoder 108 receives the optional connector 110. The PCMCIA card receptacle 114 receives the PCMCIA card 104. Finally, the controller 116 controls the entire operation of the portable information terminal.
Here, the PCMCIA card 104 has stored a new program to replace or update the existing program pre-recorded in the ROM 100 and a utility program that functions to replace or update the existing program with the new program. In order to update the ROM 100 with a new program, the utility program and the new updating program are temporarily transferred to the RAM 102.
The above-described conventional technique, disclosed in U.S. Pat. No. 5,590,373, requires special devices, such as the optional connector 110 and the connector receptacle 112, to add or update a new program to be recorded in the ROM 100 and, therefore, also requires extra expense.